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Using a DNA construct, named Lama, derived from the murine parotid secretory protein (PSP) gene, we have obtained salivary gland specific gene expression in transgenic mice. Lama is a PSP minigene and allows analysis of the PSP gene 5′ regulatory region by transgenesis. We show here that the regulatory region included in Lama with 4.6 kb of 5′ flanking sequence is sufficient to direct expression specifically to the salivary glands. The expression level in the parotid gland is only about one percent of the PSP mRNA level, while that of the sublingual gland is near the PSP mRNA level. This suggests significant differences in the PSP gene regulation in the two glands. In addition, Lama is a secretory expression vector in which cDNAs or genomic fragments can be inserted. We demonstrate that the Lama construct can direct the expression of a heterologous cDNA encoding the C-terminal peptide of human factor VIII to salivary glands and that the corresponding peptide is secreted into saliva.

The elongation factor la (EF-1α) is a protein which promotes the GTP-dependent binding of aminoacyl tRNA to ribosomes in the protein synthesis process. A human gene coding for EF-1α has previously been cloned and sequenced along with a pseudo-gene [1]. Here, we have further analyzed the family of human EF-1α genes. Using an EF-1α cDNA as probe twelve genomic EF-1α-like clones were isolated and analyzed. Four of these were sequenced and found to contain EF-1α retropseudogenes. A Southern blot analysis indicated that the remaining eight clones also contained retropseudogenes. Genomic Southern blot analysis revealed at least twenty loci in the human genome with sequence homology to the EF-1α cDNA. Besides the already described active gene only one potentially active locus was found. The others appeared to be retropseudogenes. EF-1α retropseudogenes were also found to be abundant in the mammalian species mouse and pig, while the chicken contained only one presumably active EF-1α gene.

PSP is the most abundant translation product of mouse parotid glands where its production is co-ordinated with that of salivary amylase. The synthesis of these two proteins apparently is restricted to this tissue. In order to enable us to study common regulatory elements in the genes of the two proteins, double stranded cPNA, synthesized for parotid gland poiy (A)+ RNA, was cloned. DNA sequencing of three clones complementary to the most abundant messenger indicated overlap and resulted in a total sequence of 867 nucleotides. Translation of this sequence revealed that at one end the amino acid sequence was the same as the N–terminal sequence of PSP. The sequence contains 60 nucleotides coding for part of or the complete signal peptide, 645 nucleotides coding for the PSP protein, and 162 nucieotides that apparently are not translated. Southern blot analysis suggests a simple structure for the PSP gene in mouse and man.